1. Field of the Invention
The present invention relates to a system and a method for inspecting pattern data for an electron beam patterning system producing masks used in manufacturing semiconductor integrated circuits, and more particularly to a system and a method of comparing and inspecting patterns for comparison between design pattern data and pattern data for an electron beam patterning system generated from the design pattern data and inspection thereof.
2. Description of the Background Art
In recent years, with highly integrated, multi-function semiconductor integrated circuits, the circuit scale tends to be increased and thus there is a demand for a mask of higher quality used in the process for manufacturing semiconductor integrated circuits.
Electron beam patterning systems are commonly used for fabricating masks used in manufacturing semiconductor integrated circuits and, in particular, large scale integrated circuits (LSI), due to their good micro-lithography performance and controllability.
Pattern data for an electron beam patterning system used in the mask fabrication is generated from design pattern data. Whether or not the pattern data for the (raster scan system) electron beam patterning system matches the design pattern data is visually determined by the designer, by displaying both of the pattern data on a graphic display. With finer and larger scale pattern data, however, it is difficult to determine whether the data match by visual inspection by the designer and thus a pattern comparison device is being developed capable of automatically determine whether pattern data for an electron beam patterning system matches design pattern data.
FIG. 1 is a block diagram showing a configuration of a conventional pattern comparison device. The pattern comparison device includes a design pattern data file 101 for storing design pattern data, an electron beam patterning system pattern data file 102 for storing pattern data for an electron beam patterning system, a binary bit map generating portion 103 for generating a binary bit map from the pattern data, a reference binary bit map file 104 for storing a binary bit map generated from the design pattern data (i.e., a reference binary bit map), an inspected binary bit map file 105 for storing a binary bit map generated from the pattern data for an electron beam patterning system (i.e., an inspected binary bit map), a bit map comparing portion 106 for comparing map, and a comparison result file 107 for storing comparison results.
The design pattern data is design data for a pattern formed in a mask and is represented by a coordinate value of the profile of the pattern involved. The pattern data for an electron beam patterning system is pattern data used when a mask is exposed by an electron beam patterning system, and is provided so that a pattern is drawn by a combination of figures, such as triangles and rectangles, readily drawn with electron beam. Pattern data for an electron beam patterning system is generated from design pattern data, and precision of a pattern obtained from design pattern data is typically higher than precision of a pattern drawn by an electron beam patterning system. Thus, when pattern data for an electron beam patterning system is generated from design pattern data, an error to some extent is produced.
Binary bit map generating portion 103 divides a pattern obtained from design pattern data or pattern data for an electron beam patterning system into smaller rectangles which are binarized depending on whether the center of each rectangle is white or black. Then, each small rectangle is used as one pixel to make the respective patterns into bit maps. The produced binary bit maps are stored into reference binary bit map file 104 and inspected binary bit map file 105, respectively.
Bit map comparing portion 106 compares the inspected binary bit map with the reference binary bit map to detect and store any non-match portion into comparison result file 107. The designer displays the non-match portion on a graphic display to determine whether the pattern data for an electron beam patterning system matches the design pattern data.
FIG. 2 shows a reference binary bit map generated from design pattern data, an inspected binary bit map generated from pattern data for an electron beam patterning system, and a result of comparison between the two bit maps. Design pattern data 108 is binarized and made into a bit map in binary bit map generating portion 103 to generate a reference binary bit map 110. An inspected binary bit map 111 is similarly generated from pattern data 109 for an electron beam patterning system. Bit map comparing portion 106 compares inspected binary bit map 111 with reference to binary bit map 110 to generate a comparison result 112, wherein 0 represents a match portion and 1 represents a non-match portion. Thus, it can be seen that when the position of design pattern data 108 is only slightly different from the position of pattern data 109 for an electron beam patterning system, a non-match portion is generated within comparison result 112.
FIG. 3 shows a reference binary bit map generated from design pattern data, an inspected binary bit map when a sizing processing is applied to pattern data for an electron beam patterning system, and a result of comparison between the bit maps. For pattern data in which more portions are irradiated with electron beam, pattern data in which less portions are irradiated with electron beam, or pattern data in which adjacent pattern data are closely arranged, it is necessary to enlarge or reduce the design pattern data in generating pattern data for an electron beam patterning system from the design pattern data, in order to prevent degradation of the quality of a pattern formed in a mask. The enlarging or reducing processing is referred to as a sizing processing.
Design pattern data 108 is binarized and made into a bit map at binary bit map generating portion 103 to generate a reference binary bit map 110. Meanwhile, a sizing processing is applied to pattern data 109 for an electron beam patterning system generated from design pattern data 108 to generate enlarged pattern data 113 from which an inspected binary bit map 114 is then generated. Bit map comparing portion 106 compares inspected binary bit map 114 with reference binary bit map 110 to generate a comparison result 115. A sizing process is thus applied to pattern data 109 for an electron beam patterning system to find any non-match portion generated within comparison result 115.
Furthermore, a vector scan system electron beam patterning system is used in mask fabrication in the frontiers of technology. A position to be irradiated with electron beam for a vector scan system electron beam patterning system can be the inverse of a position to be irradiated with electron beam for a raster scan system electron beam patterning system and thus black-white inversion need be applied to the design pattern data.
FIG. 4 shows a reference binary bit map generated from design pattern data, an inspected binary bit map when black-white inversion is applied to pattern data for an electron beam patterning system, and a result of comparison between the bit maps. Design pattern data 108 is binarized and made into a bit map at binary bit map generating portion 103 to generate a reference binary bit map 110. Meanwhile, black-white inversion is applied to pattern data 109 for an electron beam patterning system generated from design pattern data 108, to generate pattern data 116 from which an inspected binary bit map 117 is then generated. Bit map comparing portion 106 compares inspected binary bit map 117 with reference binary bit map 110 to generate a comparison result 118. Thus, black-white inversion is applied to pattern data for an electron beam patterning system to find any non-match portion generated within comparison result 118.
As described with reference to FIG. 2, with a conventional pattern comparison device, even a slight difference caused in generating pattern data for an electron beam patterning system from design pattern data which does not substantially affect the quality of a mask is identified as a non-match portion and thus confirmation operation by the designer is disadvantageously increased.
Furthermore, with a conventional pattern comparison inspection system, as described with reference to FIG. 3, a sizing processing need be applied to design pattern data for the improvement in finished precision of a mask. Thus, when pattern data for an electron beam patterning system after a sizing processing is compared with the design pattern data, most of the portions are disadvantageously identified as non-match portions.
Furthermore, as described with reference to FIG. 4, when a vector scan system electron beam patterning system is used for mask fabrication, all of the portions of a comparison result can be identified as non-match portions and thus conventional pattern comparison devices cannot be applied.